Road traffic-induced particle matter dispersion in a calm wind environment at the main roundabout in Douala, central Africa

Introduction: Road traffic emissions are among the most significant sources of pollution in Douala, Cameroon's economic town, alongside industrial operations. The morning and the evening are two times of the day when traffic is heavier and the winds are also at their calmest. The majority of the non-exhaust Particulate Matters (PMs) produced by autos is re-suspended road contaminants. The purpose of this research is to estimate fine particle dispersion in conditions of calm winds. Materials and methods: In one of Douala's roundabouts, the Gaussian Plume model is employed to calculate the PM concentration under calm winds conditions. Different vehicle classes (HDV: Heavy Duty Vehicles, LDV: Light Duty Vehicles, PC: Passenger Cars) are used to figure out the amount of PMs they produce. Measurements of ambient fine particle concentrations are made with the OC-300 laser dust particle detector. Results: The results made it possible to compare actual measurements of PM2.5, PM10 (300±150 µg/m3 and 650±150 µg/m3 , respectively) with simulated values (PM2.5, PM10: 310 µg/m3 and 631 µg/m3 , respectively). The difference between in-situ and computed values can range from 10 to 132 µg/m3. From 6 to 10 AM, the population's exposure to PM pollution is more severe. It has also been demonstrated that there is a significant association between traffic flow and PM Concentration during the dry season (R2=0.921). With increased traffic flow intensity, particle concentration levels rise. Conclusion: The concentration threshold stays above the World Health Organization (WHO) limits regardless of the approach. Furthermore, this paper provides important information about Douala's pollution levels.